1. Field of the Invention
The present invention relates to a protection structure for a flexible flat cable which is arranged in a single layer or laminated in multiple layers between a fixed member and a movable member which is movable relatively to the fixed member.
2. Description of the Related Art
The flexible flat cable (hereinafter referred to as "FFC"), which has an excellent property for bending or sliding, has been used for the purpose of power supply from the fixed member to the movable member.
However, the FFC itself has no lap. Therefore, if the movable member is repeatedly moved in a two-dimensional arrangement, the FFC may buckle, easily deform owing to any external force and wear. This reduces the life of the FFC greatly. In order to overcome such an inconvenience, several proposals have been made.
For example, in JP-A-10-936, a structure for protection of a harness for power supply (signal line and driving line) is proposed which is arranged in a slide door adopted in a side door of a box type vehicle called "one box car".
This structure intends to overcome difficulty for a long time due to several causes such as swing, twisting, buckling, etc. Referring to FIGS. 6-11, an explanation will be given of the proposed structure.
FIG. 6 shows an entire configuration of the structure for harness protection in a sectional view of a vehicle.
In FIG. 6, reference numeral 130 denotes a car body which is a fixed member; and 102 denotes a slide door which is a movable member. The slide door 102 is provided with a lower arm 121 which extends toward the side of the car body 130. The lower arm 121 is provided with a side roll 122 and a guide roll 123 at its end.
On the side of the car body 130, a lower rail 125 is formed. On the ceiling 126 of the lower rail 125, a guide groove 127 is formed. The guide groove 127, in which the guide roll 123 on the side of the slide door 102 is fit, limits the movement of the slide door 102 in a horizontal direction in FIG. 6. The side roll 122, which is placed on the floor 128 of the lower rail 125, can support the weight of the slide door 102 on the side of the car body 130.
The one end of the flexible conductor 140 is attached to the lower arm 121 on the side of the slide door 102 whereas the other end of the flexible conductor 140 is attached to a back wall 129 of the lower rail 125 on the side of the car body 130.
As shown in FIG. 7 which is a perspective view of the lower arm 121 and flexible conductor 140, the above one end of the flexible conductor 140 is coupled with an L metal fitting 141 through an end plate 152. The L metal fitting 141 is tightened onto the above end of the lower arm 121. The other end of the flexible conductor 140 is tightened to the back wall 129 (FIG. 6) through an end plate 148.
As seen from the front view of FIG. 8, the flexible conductor 140 includes a wiring portion 145 on the car body side, a narrow flexible conductor 146, an end plate 148 which bends an internal wiring at 90.degree. and makes holes 147, a wide flexible conductor 149, an end plate 152 which makes bolt holes 151 on the door side. The section of the main part is structured as shown in FIG. 9.
The narrow flexible conductor 153, as shown in FIG. 9, includes six signal lines 155 and two driving lines 156 which are fixed by resin laminate 157 in a state where they are arranged in parallel. The wide flexible conductor 149, as shown in FIG. 10, includes six signal lines 155 and two driving lines 156 which are fixed by a flexible resin belt 158 in a state where they are arranged in parallel. It should be noted that the flexible resin belt 158 is approximately twice as high as the resin laminate 157.
FIG. 11 shows another example 150 of the wide flexible conductor. The wide flexible conductor 150 includes the narrow flexible conductor 153 and two thin resin plates 150a bonded on both sides thereof.
An explanation will be given of the effects of the flexible conductor when the slide door 102 is opened or closed.
The flexible conductor 140 shown in FIG. 8 is bent in a U-shape when viewed in plan (FIG. 7). The one end thereof follows the movement of the slide door 102 while its bending position varies.
In this case, since the flexible belt 158 (FIG. 10) is about twice as high as the resin laminate 157, it has an extremely large sectional coefficient and sectional secondary moment. Therefore, the flexible belt 158 is difficult to warp and loose shape.
The flexible belt 158 overlaps the vertical wall of the guide groove 127 in contact with each other (FIG. 6). Therefore, even if the flexible conductor 140 is horizontally inclined slightly when the slide door 102 is opened or closed, it does not come off the guide groove 127.
Further, even if the bottom of the flexible belt 158 wears owing to its sliding friction with the floor 128 (FIG. 6), the signal line 155 and driving line 156 (FIG. 10) are not naked.
In order to protect the signal line 155 and driving line 156 when the slide door 102 is opened or closed, the prior art shown in FIGS. 6 to 11 adopts the structure of fixing these lines by the resin laminate 157 and the flexible belt 158.
However, in such a structure, it is necessary to assure a sufficient space for arranging the flexible belt 158 in a vertical direction of a car. Such a space can be assured in the lower rail 125 (FIG. 6) on which the side roll 122 moves. The structure according to the prior art cannot be applied to all mechanical components.
In addition, it is guessed that the flexible conductor 140 as shown in FIG. 8 is manufactured by individually resin-molding the respective components, i.e. narrow flexible conductors 153, 146, wide flexible conductor 149, and end plates 148, 152. This technique requires a large number of man-hours, thus leading to increase in cost.
Further, the wide flexible conductor 149 is difficult to warp as described above and the rigidity thereof is also unbalanced in its width direction. Therefore, when the opening/closing operation is repeated, the flexible conductor 149 becomes deformed gradually. This may interfere with power supply to and the opening/closing operation of the slide door 102. Furthermore, the flexible conductor 149 does not have the excellent bending or sliding characteristic like a flexible flat cable which have been widely used.
In the future, it is expected that the number of the signal lines is increased owing to necessity of various kinds of signals to be transmitted to the slide door 102. This requires the design to be changed for assuring the arranging space in a vertical direction of the car.
Thus, the above prior art, which intends to protect the signal line 155 and driving line 156 in a manner of fixing them using the flexible belt 158 or the like, encounters the various problems described above.
Accordingly, it is demanded to provide a new protection structure for lengthening the life of the flexible flat cable using its advantage.